Signaling means for training devices



March 22, 1949; T. J. MCLAUGHLIN 2,465,165

SIGNALING MEANS FOR TRAINING DEVICES Filed May 18, 1944 5 Sheets-Sheet 1 THOMAS J. MCLAUGH LIN INVEN TOR.

ATTORNEYS.

March 22, 1949. T. J. McLAU GHLlN 2,465,165

SIGNALING MEANS FOR TR AINING DEVICES Filed May 18, 1944 5 Sheets-Sheet 2 IIIIIIf/IIIIIIIIII!lI'I/IIIIIIIIIIII v HQ 3 THOMAS J. MCLAUGHLIN ATTORNEYS.

March 22, 1949.

T. J. M LAUGHLIN SIGNALING MEANS FOR TRAINING DEVICES 5 She'ets-Sheet 3 Filed May 18, 1944 e .n v m R2 31 THOMAS J. M LAUGHLI N INVENTOR. W [/M w EOPOS Anonuzvs.

T. J. M LAUGHLIN SIGNALING MEANS FOR TRAINING DEVICES March 22, 1949.

5 Sheets-Shea; 4

Filed May 18, 1944 THOMAS JQMCLAUGHLIN I INVENTOR.

BY M6? 0% "WW I ATTORNEYS.

Patented Mar. 22, 1949 SIGNALING MEANS FOR TRAINING DEVICES Thomas J. .McLaughlin, BinghamtomflN'. Y.,as-

signor'to Link Aviation, Inc., a'corporatio'n of New York Application May 18, 1944, Serial N.-53.6;120"

7 Claims.- (Cl. 34 3-.-101) My invention relates toan aviation trainer, and particularly to means for training pilots in the art of navigation by radio;

Radio aids have proved to be of great and in! creasing value to the navigator. Amon the most important of these radio aids are the signals sent out "by those stations commonly referred to as radio range stations. Each radionrange station transmits a pattern marking. four courses, normally 90 apart, although this spacingis often varied inv order that'oneror more of the courses will coincide with an established airway. This system generally utilizesttwo pairs of transmitting towers which transmit interlocking Morse code signals. For instance; one pair. of towers maybe transmitting directionally theletter A. while the others'pair transmits the letter N the timing beingsynchronized so that at all times-one pair 01% towers is transmittin a signal.

This arrangement produces the result that in any two diagonally opposite quadrants,--as seen in Fig. 1, the Asignal is heard clearly and the N signal is of a lesser intensity ords not heard at all, depending-upon how far the plane is human N quadrant. In the other pairofdiagonally opposite'quadrants, the relative intensities of the letters are reversed.=. Each quadrant slightly overlaps the neighboring ones and in the narrow wedge of about. 3 that 'forms the center of the overlap -the A and N signals are heard'with equal intensity so the .dots and dashes of the two sig-- nals interlock to produce a continuous-tone. This 1 is thefamiliaron-course signal.

TheseA-N signals are interrupted .abouttwice eachiminute for .the transmission of two sets of stationidentifying signals. The first set of these identifyingsignals is always transmittedin the N quadrantsby the N towers and the second set in the ,A quadrants by the A- towers.

the N signal.( and'the first station identification. signal, butwill not hear. the A signal nor the second station identifying signal which is transmitted into the A quadrants.

If he is on course, he will hear a dash about 25 seconds long, caused by the interlocking of the A and N signals, followed by .the two sets of identifyin signals, the first of which is transmitted signal is the weakerythe pilotkn'owsthat"he is.

If a'pilot is. near the bisector of an-N quadrant, he will hear.v

in an A quadrant' while=Lif theAsignal andthea: second station identification. signal. is theweakeigi he knows he is inan N quadrant: Difierentra'ngei stations transmit ondifferent carrier"frequencies; but these audible signals: are al-Waysof .thesam'e frequencmsnamely;1020.1'cycles per second.

The pilot, radio Jmanor navigator of. la planer; by intercepting the signals. being transmitted: by: such'a radio range station will therefore ibe'able to tell whetherthe planeis in an A quadrant,:an:i

N quadrant or on one of the on-course" beams.

By maneuveringth'e plane and-noticing the effects of the maneuvers upon the intercepted signals? the pilot is able to locate the position of. the plane in the radiatedfield patternrof. the radiorange station and; inasmuch as he has in'the plane witht; him amap ofithe em'anatedfield pattern of then station; he canuascertain .the geographical. posis' 'tion'of. the ship.

In the instruction. ofustuclentsto flyv byimeansx. of :the signals transmittediby these 'radiorange:- stati'ons'it has been found particularlydesirable.- to combine with a traineriof the type disclosed.

in U. S. Patents 1,825,462 and 2,099.857,"means' whereby simulated: radio range signals may be transmitted to the student in the trainer who, by

interpreting the simulatedsignals received; 'navi-"- gates the trainer in the same manner'that he would actually navigate a realplaneby'means of actual radio rangesignals. Such'means are-dis closed in U. S; Patent 2,119,083.

It is common practice in theprior artto-com' bine with such .a trainer a recorder of the type signal field. The student in the trainergby chang ing the-headin of the fuselage in 'responsef-to the simulated radiorange signals received by him controls the direction of the recorderstravel; and the recorder traceson' the map'the assurn'edtrack of the trainer through the assumed 'radiorange signal field. The instructor in turn transmits signals to the student in the trainer in accord ance with'the observed position'o-f the recorder;

upon the map, .yhich'position represents the as.-

sumed positionof the trainer in an assumed radio" range signal pattern.

Means under the manual control'of the in structor whereby he can transmit A-N signals of varying relative intensities and of Varying absolute intensities to the student in the trainer in accordance with the moving position of the recorder over the map are disclosed in United 'States Patent Number 2,119,083. However, such a system has several disadvantages. First, such a system requires the constant close attention of the instructor. Secondly, the instructor at all times must estimate the desired relative intensities of the A-N signals as well as the proper absolute volume to be given these signals, and then he must manually set the controls in the positions which he believes will give the estimated desired signal intensities. In order that the constant attention of an experienced instructor may be dispensed with, and in order to eliminate the inevitable errors of judgment upon the part of the instructor, it is highly desirable that there be automatic means for changing the relative as well as absolute intensities of these A-N signals heard by the student in the trainer as the recorder changes its position upon the map. To meet this need devices known to the art as automatic radio ranges for grounded aviation trainers have been devised. These devices generally comprise means for establishing a quadrantal field of force keyed by A and N signals in simulation of the keying of the quardants of a real radio range.

The keyed field of force is generally established below a smooth surface over which the recorder travels and an element responsive to the .field of force is carried by the recorder and connected to suitable amplifying and receiving means which feed into the earphones of the student in the trainer. Therefore the signals received by the student depend upon the position of the recorder in the keyed field of force and he manipulates the trainer in response to the signals received to govern the direction of travel of the recorder just as-he would control a plane in actual flight flying through a real radio range in response to the signals received.

It is a principal object of this invention to provide means whereby the miniature field of force which normally transmits A and N signals may be periodically interrupted and the fields of force properly keyed according to an assumed station identification signal in simulation of the corresponding practice outlined above employed in connection with real radio ranges.

As a plane in actual flight through a real radio range signal pattern approaches the station from a distance a gradual increase in the intensities of the intercepted signals occurs until the plane is a short distance from the transmitting towers. When this point is reached a sudden and greatly increased intensity of the intercepted signals occurs and immediately thereafter for a short distance in some real radio ranges no signal is intercepted. This area of no signal reception is commonly known as the cone of silence. However other radio ranges employ an auxiliary transmitter which transmits upwardly a steady note of 3000 cycles in a pattern to fill the otherwise present cone of silence. With this arrangement therefore the receiver in the plane instead of receiving no signal when in the cone of silence will receive the steady 3000 cycle note. This arrangement, known as a positive cone of silence, is employed in order that any possible fading of signals at a point other than above the cone of silence will not be mistaken by the pilot for the cone of silence.

As the plane continues over the cone of silence or positive cone of silence, as the case may be. the extremely high level signal is again encountered. Continued travel outward from the cone results in a rapid attenuation of signal level in a manner inverse to that experienced upon approaching the cone.

It is another principal object of this invention to provide separate elements properly keyed and fed with a high voltage to produce means for simulating the just described high level signals. These separate high voltage elements are preferably mounted as will be later disclosed so that they may be adjusted in accordance with the on-course signal areas of the automatic radio range.

Also in real radio ranges there is provided means whereby the station operator may if desired transmit oral intelligence at the same time that the towers are transmitting the A-N and station identification signals. This oral intelligence for example may be weather reports. At the same time radio receiving sets carried by planes in actual flight generally embody a threeposition switch under the control of the operator of the receiving set. By selectively positioning the switch the receiver operator may cause filters in the receiving set to cut out the A-N signals allowing the oral signals to come through or he may cut out the oral signals allowing the A-N signals to come through. Further he may receive both types of signals.

Again, referring to real radio ranges for the purpose of comparison, upon the ground below, one or more of the on-course signal areas and located a few miles from the main transmitting towers an auxiliary transmitter known as a fan marker beacon may be placed. These beacons transmit upwardly a fan shaped signal pattern, the signal having a frequency of 3000 cycles per second and the signal is keyed in a pattern of l, 2, 3 or 4 dash groups in order that the fan marker may be identified with a particular leg of the range station. Upon the hearing of this signal the pilot of a real plane knows that he is above one of the fan markers of the range station, and further, by noting the manner of keying of the signal he will be able to ascertain his exact location.

Another object of this invention is to provide cone shaped quadrantal plates for establishing the desired pattern of the automatic radio range, each of the cone shaped plates being connected by a conductor to an arcuate segment that is positioned at the base of each of the cone shaped segments. upon a cone shaped supporting block and the arcuate segments upon a flat member upon which the cone shaped block is placed. A suitable insulating block is placed at the apex of the cone shaped plates, this block holding the plurality elements which are fed by a higher potential than the cone shaped plates. This arrangement produces the desired changes in signal intensities as the recorder and pick-up antenna moves above the quadrant assembly.

In order that this invention may be more readily understood reference is made to the accompanying drawings which illustrate a preferred embodiment of the invention. In the figures,

Fig. 1 is a general view of an aviation trainer of the type hereinbefore mentioned, the instructors desk, the recorder mounted upon a chart of a real or assumed radio range and the gem The cone shaped plates are mounted eral location of the quadrant plates of this invention relative to the chart and recorder.

Fig. 2 is a plan view of the quadrant assembly.

Fig. 3 is a cross sectional view of the quadrant assembly taken along the lines III--III of Fig. 2.

Fig; 4 is a diagrammatic wiring diagram of the signal generating means.

Fig. 5 is a diagrammatic view of the quadrant assembly and electrical connections thereto.

Fig. 6 is a detailed view of the inking wheel and a part of the recorder, certain parts being cut away for purposes of illustration.

Fig. 7 is a cross sectional view of the shaft holding the inking wheel.

Fig. 8 is a diagram in block form of the audio receiver.

Fig. 9 is a detailed view of the fan marker simulating means.

Fig. 10 is a detailed view of a part of the quadrant assembly.

Figs. 11 and 12 are front and rear elevations, respectively, of the quadrant assembly.

In Fig. 1 the numeral I0 designates generally a trainer of the type hereinbefore mentioned. This trainer comprises a fuselage I2 which is universally mounted upon a base I4 by means of an intermediate universal joint (not shown). By means of conventional airplane simulating controls the student in the trainer may cause the fuselage to bank to the left or right as well as to climb and dive, in simulation of the corresponding movements of a real plane in actual flight. A turning motor I6 is provided and by means of a pair of simulated rudder pedals within the fuselage I2 the student may cause the trainer to turn to the left or right about its vertical axis in simulation of the turning of a plane in actual flight.

The desk is numbered l8 and upon the top 24 of the desk is placed map which shows the radiated field pattern of a real or assumed radio range station. Recorder 22 rests upon map I6. This recorder, as previously stated, travels over map 20 at a rate proportional to the assumed ground speed of the trainer and its direction of travel over the map is at all times in accordance with the assumed direction of travel of the trainer over the ground. This recorder comprises a pair of propelling wheels 23 (only one shown), and inasmuch as the recorder covers a considerable portion of map 20 the trainer is assumed to be located at the exact spot where the inking wheel 25 rests upon the map.

The top 24 of desk I8 is preferably made of an insulating material such as wood, Bakelite or glass. Beneath the top 24 of the desk is placed the quadrant assembly designated generally 26, this quadrant assembly resting upon a wooden base supported by guides 28.

Reference is now made to Figs. 2 and 3 which are views of the quadrant assembly and associated parts designated generally in Fig. 1 by 26. Referring to Fig. 2 the wooden base 30 is provided and four quarter circle arcuate plates 32, 3'4, 36 and 38 are attached to base 30 by means of screws 40. A pair of openings 3I are provided in base 30 for ease in removing the same from desk I8. Referring to Fig. 3 a cone shaped block 42 made of suitable insulating material such as wood is fixedly attached to base 30 by means of screws 44 and four quarter cone-shaped plates 46, 48, 50 and 52 are affixed to block 42 by means ofscrews 54-. A jumper 56 connects arcuate plate 32' with its corresponding cone-shaped plate 46' by means of screws 50, the inner ends of which 6 enter block 42. Similar jumpers 60, 62 and 64 connect the other three sets of arcuate plates with their corresponding quadrant cones in the same fashion. By virtue of this jumper arrangement it will be understood that any charge applied. to one of the quarter cone-shaped plates will be applied at the same time to its corresponding arcuate plate. Consequently, for purposes of simplicity, hereinafter charging of the quarter cone shaped plates only is discussed, but it should be borne in mind that the arcuate plates are always charged simultaneously with their connected cone shaped plates.

Further, it should be noted that each of the arcuate shaped plates is separated from its adjoining arcuate plates by virtue of spaces 220, and the cone-shaped plates are similarly separated from one another so that they may be independently charged.

Quarter cone shaped plate 46 has connected thereto as seen in Fig. 3 a wire 66 covered by suitable insulating material 68. Each of the other three cone shaped sections has a similar arrangement as will be later shown.

Reference is now made to Fig. 4 which shows schematically the means for generating the signals used in this invention. Seen in Fig. 4 is rectifier I0 connected to ground I2. Amplifier I4 is also connected to ground I2 and an oscil-' lator' I0 suitably supplied with power is provided, this oscillator generating a steady 1020 cycle signal. This signal is fed into amplifier I4 by means of conductor 18 and the direct current from rectifier I0 fed into amplifier M is modulated. by the 1020 cycle voltage so that by means of conductor a 1020 cycle alternating voltage is placed across the primary 82 of the transformer designated generally by 84. The

other side of primary-8'2 is connected to rectifier 10 by means of conductors 06 and 88. Similarly by means of conductor a 1020 cycle voltage is placed across the primary 92 of the transformer designated generally by 94, the other end of primary 92- also being connected to rectifier ill by means of conductor 88. The secondary 550 of transformer 84 has one end connected to grid 98 of amplifier I00 by means of conductor I02 while the other side of secondary 9B is connected to the grid Hi4 of amplifier Hit by means of conductor I 08. The plate IIO of amplifier 500 is connected by means of conductor I I2 to one end of primary I I4 of transformer designated generally by HG while the plate H8 of amplifier Hi6 is connected by means of conductor I20 to the other side of the primary I I4. The center tap of primary H4 is connected by means of conductor I22 to the rectifier ID. The cathode I24 of amplifier I00 is connected to the cathode I20 of amplifier I 06 by means of conductor I28 and conductor I28 is connected through cathode bias resistor I30 to ground 72. Ground 12 is connected to rectifier I0 through resistor I32 and conductors I34 and I36. Resistor I32 is also connected to the center tap of secondary 96 by means of conductor I42.

It will be appreciated by those skilled in the art that the transformers 84 and H6 and amplifiers I00 and I00 comprise a conventional push-pull amplifying system and that the voltage of grids 98' and I04 change at the rate of 1020 cycles per second. By means of the current normally flowing through conductors I36 and I 34 the resistor I32 the negative bias upon grids 98 and I04 is so great that normally no plate current flows through amplifiers I00 and I00 and therefore no current flows through the primary II4 of transformer II6. Consequently no voltage is induced in the secondary I44. The upper end of transformer II6 is connected by means of conductor I46 to terminal A of plug I48. This terminal A is connected, as by a suitable cable, to terminal A of plug I50 shown in Fig. to which reference is now made. By means of conductor I52 terminal A of plug I50 is connected through potentiometer I54 and conductor I56 to pin I58, the detailed nature of which will be later described. The lower end of transformer secondary I44 is connected by means of conductor I60 to terminal D of plug I48 which in turn is connected to terminal D of plug I50 shown in Fig. 3. This last terminal is connected by means of conductor I62 through potentiometer I64 and conductor I66 to pin I88 which also will be later described. Secondary I44 is also tapped at a point intermediate its upper end and its center as seen in Fig. 4 by the conductor I10 which connects to terminal B of plug I48. This terminal connects with the terminal B of plug I50 which in turn is connected by means of conductor I12 through the rheostat I14 and conductor I16 with cone shaped section 48 to which reference has been made in connection with Figs. 2 and 3. Conductor I16 is connected to section 48 in the same manner that conductor 66 is connected to section 46 as seen in Fig. 3. Secondary I44 is also tapped by conductor I 18 which connects with terminal C of plug I 48, this terminal being connected to the terminal C of plug I50. By means of conductor I80 this last mentioned terminal is connected through rheostat I82 and conductor I84 with cone shaped plate 52. The purpose and nature of rheostats I54, I64, I14 and I82 will be later disclosed.

The center tap of secondary I 44 is connected to ground 12 by means of conductor I86.

It has been shown that normally the bias of grids 98 and I04 of amplifiers I00 and I06 is so great that no current flows through primary I I4, and consequently no voltage is induced across secondary I44. Therefore, the connections between secondary I44 and the plates 48 and 52 and pins I56 and I68 will not charge any of these last four mentioned elements. They cannot, therefore, establish an electrical field which may be picked up by a receiving antenna. Means for periodically shorting resistance I32, seen in Fig. 4, whereupon the negative bias on grids 98 and I04 is lessened so that plate current may flow through amplifiers I00 and I 06 will now be described.

Referring to Fig. 4, rectifier 10 is connected through conductor I36 to leaf I90 of switch designated generally I92. The position of leaf I90 is governed by the position of rotatable cam I94, the exact nature of which will be later described. It is sufficient at this point to state that normally cam I94 is positioned so that leaf I90 is in contact with point I96 which is connected to conductor I98 which in turn is connected to point 200.

The position of leaf 202 is controlled by A-N cam 204 and leaf 202. is connected to ground 12 by means of conductor 206.

A-N cam 204 is mounted upon shaft 208 which is turned by motor 2I0 and this cam has a P6- ripheral pattern such that leaf 202 alternately engages and disengages point 200 in a pattern corresponding to the Morse code signal for the letter A Whenever leaf 202 engages point 200 it will be understood that the direct current which normally flows from rectifier 10 through ground 12, resistor I32 and conductors I34 and I36 back to the rectifier will take the path of least resistance and instead of flowing through resistance I32 will flow to leaf I90, which normally engages contact I96, through contact I96 and conductor I98 to point 200 whence it travels along conductors 206 and 208 to ground 12. Consequently the voltage drop across resistor I32 will be eliminated and the potential of grids 98 and I 04 will be increased in the positive direction. This increase in grid potential is sufficient to allow current to flow through amplifiers I00 and I06 and therefore through the primary II4 of transformer I I 6. However, as soon as cam 204 causes leaf to be disengaged from point 200 the current through the amplifier is stopped. Inasmuch as leaf 202 engages contact 200 in the Morse code signal pattern for the letter A it will be appreciated that current flows through primary H4 in the pattern of the Morse code signal for the letter A. A voltage will be induced across the secondary I44 of transformer H6 in the same pattern and by means of the connections and taps from this transformer to the plug I48, the cable between plug I48 and plug I50 and the connections between plug I50 and the cone shaped sections 48 and 52 as well as pins I58 and I68, it will be realized that these four last mentioned elements will be alternately charged and discharged by the voltages induced in primary I44 whenever leaf 202 is in engagement with point 208. Inasmuch as cone shaped section 48 and pin I58 are connected to the upper side of secondary I44 while section 52 and pin I68 are connected to the lower portion of the secondary, the potential of the first two elements will be in phase with one another but 180 out of phase with the potential of the latter two elements. Further, the potential of the two pins will be equal and greater than the potential of the two cone shaped plates, and the potential on the two plates will be equal. Inasmuch as the voltage of grids 98 and I04 is always changing at the rate of 1020 cycles per second, whenever sections 48 and 52 and pins I58 and I68 are being charged their potential is changing at the rate of 1020 cycles er second. Therefore these elements will establish a field of force in the Morse code pattern for the signal A and whenever charged their potential is varying at the rate of 1020 cycles per second.

Reference is now made to Fig. 4 which discloses a second pair of amplifiers I00 and I06 which are identical with the amplifiers I00 and I 06. The amplifiers I00 and I06 are combined in a system having all elements identical with the system comprising amplifiers I 00 and I06. The corresponding elements of the second system are given in the drawings primed numbers corresponding to the numbers in the first system.

Cam I94 is normally positioned so that leaf I contacts point I98, and contact I96 is connected to point 200 by conductor I98. When leaf 202 is not in contact with point 200 the current from rectifier 10 flowing through conductor I36 and resistor I32 to ground 12 negatively biases grids 98 and I04 to such an extent that no plate current fiows through amplifiers I60 and I06. Therefore no voltage is induced in secondary I44 of transformer I I6 and consequently the conductors I46, I10, I18 and I60 which connect to pin I58, conical section 50, conical section 46, and to pin I68, respectively, cannot charge these last four mentloned elements. However A-N cam 204, in addition to having a peripheral pattern such as to cause leaf 202 to contact point 200 in the Morse code signal pattern for the letter A also has the peripheral pattern necessary to cause leaf 202 to contact point 200 in the Morse code signal pattern for the letter N Cam 204, leaf 202 and contact points 200 and 200 are arranged so that leaf 202 comes into engagement with the contact 200 or 200 at the instant that the leaf disengages from the other contact. When leaf 202 is engaged with contact point 200 and leaf I90 governed by cam I94 is engaged with point I96, as is normally the case, resistor I32 is shorted and the normally high bias upon grids 98 and I04 is removed so that plate current flows through ampllfiers I and I06. Inasmuch as grids 98 and I04 are energized by the 1020 cycle signal originating in oscillator I6 it will be appreciated that current flows through primary H4 in the Morse code signal pattern for the letter N and that when so flowing the voltage across this primary varies at the rate of 1020 cycles per second. A voltage having the same signal pattern and variations is therefore induced in secondary I44 and by means of conductors I46, I10, I18 and I60, shown in Fig. 4, and by means of conductors shown in Fig. bearing the primed numbers, a similar voltage is induced in pin I58, plate 50, plate 46 and pin I68. It is believed unnecessary to point out the circuits in detail because terminal A of plug I48 is connected to terminal A of plug I50, etc, and the circuits bearing the primed numbers correspond exactly with those discussed above relating to the A-charged conical sections and pins.

The Voltage induced in plate 50 is equal to the voltage induced in plate 40 but the two voltages are 180 out of phase. At the same time the voltage induced in pin I58 is equal to the voltage induced in pin I68 but is also 180 out of phase therewith. Also, the voltage induced in pin I58 is greater than the voltage induced in plate 50 but is in phase therewith and the same relationship is true of the voltage induced in pin IEO with respect to the voltage induced in plate 46.

By virtue of the disclosed arrangement the conical sections 48 and 52 and the pins I58 and IE8 are charged in the Morse code pattern for the letter A the voltage of section 48 being equal to and 180 out of phase with the voltage of plate 52 while the voltage of pin I58 is equal to and 180 out of phase with that of pin I68. However the charge of pin I58 is in phase with that of plate 48 and the same is true of pin I68 and section 52. The sections 46 and 50 and pins I68 and I58 are charged in the Morse code signal pattern for the letter N L. and the relative voltages have the same characteristics as those of the element charged in the A pattern.

Bearing this voltage pattern in mind, if a capacitive pick-up element were placed above plate 48 or 52 along the bi-sector of either of these plates the signal picked up by the element would be that of the Morse code signal pattern for the letter A. No N signal would be induced in the pick-up element. On the other hand if the element were placed above the bi-sector of either of the plates 46 or 50 the induced signal would be a pure N. However if the element were moved from the bi-sector of either of the N plates a substantial distance toward either of the A plates the N signal would still be predominant but, the closer it came toward one of the A plates the louder would be the background A signal. If the element were moved to a point directly above'one of the areas 220 which lie between the four quadrants of the assembly shown in Figs. 2 and 5 a steady 1020 cycle signal would be induced therein.

Therefore by virtue of the disclosed a paratus the movement of a pick-up element with respect to the assembly shown in Figs. 2 and 5 will result in a variation in the relative intensities of the A and N signals induced therein in the same manner that the signals received by a radio receiver in a plane in actual flight vary as the plane changes its position relative to the A and N quadrants of a real radio range.

Further, referring to Fig. 2, if the 'pick-upelement were placed at a fixed height relative to a level surface above the quadrant assembly at a point above the periphery of one of the arcuate segments 32, 34, 36 or 38 the *signa1 induced therein will be of a relatively low intensity because of the distance between the receiving antenna and the plates. As it is moved toward the center of the quadrant assembly it does not come closer to the arcuate plates, and therefore these elements do not increase the signal induced therein. However, at this time the pick-up element 25 will be coming closer to the cone shaped sectors, and therefore a slight increase in signal strength results. As the pick-up element is moved above the cone shaped Sectors and inwardly further toward the center of the quadrant assembly, inasmuch as the distance between the conical sectors and the element will be more rapidly decreased the signal induced therein will increase more rapidly. When it closely approaches any one of the four pins I58, I68, I58 or I68 the higher voltage applied to these pins together with the fact that they are elevated above the highest point of the conical shaped plates results in a marked increase in the voltage induced in the element until it reaches the point in the center of the square formed by these four pins. At this point the equal and opposite voltages induced in the pick-up element result in a complete cancellation of voltages induced therein. As the element moves toward another of the four pins a high voltage will be induced therein and as it passes over the pin the induced voltage rapidly drops until it comes above one of the plates 46, 48, 50 or 52. As it moves outwardly toward the periphery of the quadrant assembly the intensity of the voltage induced in the element decreases in a manner inverse to that described when the antenna was traveling toward the center of the quadrant assembly.

The disclosed apparatus therefore provides an arrangement whereby the voltages induced in a capacitive pick-up element moving over a horizontal surface placed above the quadrant assembly will be varied, in simulation of the manner that the signals intercepted by a real radio received in a plane flying through a real radio range vary in intensity as the plane changes its distance from the transmitting towers of the real radio range.

A preferred type of pick-up element and means for connecting it to an audio receiver whose output varies directly with the strength of the voltages induced therein will now be disclosed.

Reference is now made to Figs. 1, 6 and 7 which disclose an improved type of pick-up element which is a part of the preferred embodi- 11 ment of this invention. In Fig. 1 the recorder is designated 22 and the propelling wheels by 23. The inking wheel of the recorder is designated 25. Reference is made to Figs. 6 and 7 which show the inking Wheel 25 mounted in the lower end of vertical shaft 222 which is turned by main gear 21. The inking wheel is rotatably mounted upon a horizontal stud 224 which is held by an insulating bearing 226. A pair of shielded Wires 228 and 230 are soldered to the ends of the stud 224 and each of these wires has its upper terminal affixed to the slip ring 232 which is suitably insulated from shaft 222. Brush 234 engages slip ring 232 and is fixedly held to bracket 236 which in turn is rigidly aflixed by screws 238 to the bearing housing 249 which in turn is attached to the housing 242 of the recorder by means of screws 244. Shield 245 connected to the recorder surrounds the upper part of shaft 222, the slip rings and brushes. The conventional azimuth scale 246 and pointer 248 are provided at the top of recorder 22.

A second slip ring 249 is mounted on shaft 222 and is engaged by brush 25] which is suitably grounded. This arrangement therefore grounds shaft 222 and, in addition, recorder 22 is suitably grounded. Inking pad 253 is positioned in slot 255 in shaft 222 and is held by transverse stud 251 which is movable in slots 259 in shaft 222. This inking pad arrangement is highly desirable because the conventional inking pad clasp arrangement would result in distortion of the signals picked up by the inking wheel.

Brush 234 is connected by means of conductors (not shown) to'the preamplifier 258 which is attached to' the underside of recorder 22. This preamplifier is connected by means of cabl 252 which, as seen in Fig. 1, extends generally upwardly and is carried by means of tube 254 to the audio receiver in desk I8. The audio receiver is connected by means of wires in cable 255 to the student's earphones in fuselage 12. The audio receiver is schematically shown in Fig. 8 to which reference is now made. In Fig. 8 the inking wheel is designated 25, this inking wheel serving as the capacitive pick up element. The inking wheel is connected to th recorder preamplifier 258 which by means of the cable 252 is connected to th range amplifier 260. Range amplifier 260 is connected by means of conductor 262 to range relay 264 which in turn is connected by conductor 266 to mixer amplifier 268. This mixer amplifier is connected by conductor 210 to power amplifier 212 which in turn is connected by conductor 214 to the students earphones 216 which are in fuselage l2. By virtue of this arrangement therefore the voltages induced in the pick-up wheel 25 as the pick-up wheel is carried by the recorder over map 28 above the quadrant assembly 26 are translated into audible signals which are heard by the student using earphones 216. The signals heard will depend upon the position of inking wheel 25 above the quadrant assembly as previously described, and, of course, the position of the inking wheel depends upon the maneuvering of fuselage 12 by the student therewithin. The student within the fuselage [2 may therefore fly the fuselage l2 in response to the simulated radio range signals received just as a pilot in a real plane files the plane in response to the real radio range signals intercepted, and in turn, the signals heard by the student depend upon the position of recorder 22 which is governed by fuselage l2.

It should be noted that the means of transmis 12 sion from the quadrant assembly 26 to the inking wheel 25 is capacitive in nature.

A suitable volume control 218 under the control of the student is connected by conductor 219 to range amplifier 266 whereby he may adjust the intensity'of the signals received by him just as a pilot in actual flight may adjust the volume control of his radio receiver.

It has been pointed out above that real radio ranges are equipped with voice transmitting facilities whereby the operator of the range may transmit oral intelligence as the occasion arises. This feature of real radio range navigation may be simulated by virtue of the provision of the microphone 288 which is under the control of the instructor. Microphon 286 is connected to the movable contact 282 of switch designated generally by 284 and when contact 282 is engaged by the instructor with point 286 which is connected to conductor 288, the voice signals are carried to voice amplifier 298 which is connected by conductor 292 to the voice relay 294. This relay is connected by conductors 296 and 298 to the mixer amplifier 268 which, as previously disclosed, is connected through amplifier 212 to earphones 216. The instructor may therefore give simulated weather reports, etc., to the student in the trainer in simulation of the transmitting of weather reports by the operator of a radio range station.

It is to be noted that the oral intelligence transmitted by microphone 280 does not pass through the quadrant assembly 26 but is combined with the A-N signals at the mixer amplifier 268. Inasmuch as in a real radio range the oral signals intercepted by the radio receiver are directly proportional in intensity to the intensi ies of the A-N signals, it will be realized that it would be advantageous to provide means whereby the oral signals transmitted by the instructor by means of microphone 288 have, when received by the student, an intensity corresponding to the intensities of the A-N signals. In order to accomplish this desired function, part of the voltage output of range amplifier 260 is fed by means of conductor 380 to amplifier 302 from which conductor 304 leads to rectifier 396. The rectified current will have a strength proportional to the intensity of the A-N signals passing through range amplifier 260, and this rectified current is fed by means of conductor 388 through a conventional time delay circuit 3H! which connects with voice amplifier 290 by means of conductor 3l2. The output of the time delay circuit is used to bias the grid of the tubes of the voice amplifier 290, and consequently the strength of the voice signals ori inating at microphone 280 and carried by Way of voice relay 294 to mixer amplifier 268 and power amplifier 212 to the earphones 216 will be directly proportional in intensity to the intensities of the A-N signals heard by the earphones 216.

The time delay circuit 3| 8 is necessary in order that the silent periods in the A-N signals passing through range amplifier 260 will not result in sudden changes in the intensity of the oral signals in a pattern corresponding to the intermittent A-N signals.

It has been stated that real radio receivers used by planes for navigation by radio are equipped with filtering means under the control of the operator of the radio whereby he may filter out either the A-N signals or the oral signals being transmitted by the radio range station operator. The following means are incorporated -such..instructions as he desires.

eases m positioned within. fuselage I2 to be. underithe control of the student. 'When the selector'button i 3I6 of .thiszswitch'is placed in the leftmostposition in Fig. 8, by means of conductor 32Ilrange relay 264 is operated to open the circuit between =rangeamplifier ZGII and mixer amplifier 268 and ''the A-N signals are not heard by the student using the" earphones 215.

On the other hand, if:selectorizbuttoniilfi. is placed in the rightmost pos'itionxin Fig. 1:8,:by

means of conductors 326 and 322 voice. relaya294 4 is operated to break the circuit between voice am- .iplifierl i9ll and mixer amplifier ZGB'and theoral signals being. transmitted by the instructor :using :amicrophone 289 will not be heard by the-1331311- :zdent .using' earphones 2:18

.' Further when selector button3l6 is'in..theI-position shown in Fig. 8, neither voice relay 294rnor wrange relayi 264 breaks the-circuit; respectively ncontrolled-zbyit, and, therefore, earphones? 2e18 owillibe. responsive. to the "A N' signals-.picked'iup v:by inking wheel as-Well as those'originatingzat microphone lilll.

i Intthezevent-the studentin fuselage |2.'.h3.3'. se- 1 elector? button 3 I 6 in the rightmost positioniin itloned so': that contact 282 engages point::286,uif

eithe Iinstructor-. desires to talk to .the studentithis woicezsig-nalscannot reach earphones 218. Cona,sequently by placingcontact 282 in engagement iWith. point-324 which is connectedrby conductor ,326. through 'volume control 328. and 1 conductor $298150 the-=mixer amplifier 168, the instructor smay communicatewith-the student using 'earcphones 216. It should be noticed that the stu- -.dent has no control over this circuit andthere- 1 fore .the instructor mayt-at' any time give him However it, is

contemplated that the instructor will use this ,last describedoommunicating system-only in the ,eve'ntthat he-wishes to talk to thelstudent con- .cerning matters which wouldnot"normally-be transmitted over a real radio range. For'exam- .ple,.he. might desire to correct the student regarding. certain procedures that he is making in the flying of the fuselage I2.

A microphone-332 for the use of the student in the" fuselage .I2 is connected by conductor334 "to the. contact 282 so that the student-may; talk j.to 'the instructor using .the'. earphones 336 which initurn are connected .to conductor 214. by con-.-

"du'ctor 215.

.A. noise generator 338 which' preferably com- .prises suitable leads connected to anysavailable power line is provided, this generatonbeing con- ".nectedbyconduct0r 340 tov a noise control tube- "946. "Thenoise oontroltube is-..connected'1=by means of. conductor 348 to -mixer-= amplifier 268 'and it should. be noted that the .volume ofv the *noisesource is controlled bythe students vol- E'HmQCOHtIOI, 218" by virtue ofconductorsiliiyand II"to 'keep' the. noise. level commensurate with the 'sign'al.level, just as-the. case .in real radio reception. In this manner. suitable interference maybe introduced into the system to simulate "the static heardlxby the operator'of a.-r'adio.5re-

.%. Fig.:8 and the instructor has; switch; 284-posi;

taT-he .detailed: circuits of the various elements :disciosedzin. block diagram form in. Rig. 8- arenot given because this invention does not residenin the detailed construction of any of these units but rather in the novel combination of units individually well known to the prior art. Guided .by the block diagram form shown in Fig. 8-, any 'person skilled in the field of radio may arrange -:detailedcircuits to satisfactorily accomplish all sof thespreviously described functioning of the apparatus shown in Fig.8.

-It has been previously stated that. periodically the-A-N signals transmitted by real radio ranges are interrupted for the transmission of station identification signals. In real radio range prac- ...tice two sets of. station identification signals are transmitted, the first set being transmitted by the towers which transmit the N si nals so that they ..are heard at-any point in the range with an intensity equal. to that of the N signals. The second. setis transmitted bythe A towers and are heard at any, pointwithin the range with the same intensity as are theA signals.

' Referring again to Fig. 4 means-are there disclosed '-for causing the quadrant assembly .to

transmit station identification signals, thefirst set :being' transmitted bythe. N plates and pins and the second setby the A plates and pins. Cams "I94 and I94 are of a suitable three step type and are fixedly mounted upon shaft 352 which is 1 connected to the shaft'1298 by any suitable type :ofre'duction drive such as-aratchet. ar- "rangement.

Shaft 352 is arranged to make one rotation for eacl'r'fourteen rotations of shaft 298 and A-N ShaftlIiB is. driven by motor ZIIl.

cam-2M. The. three step, peripheral pattern of cams I94 and I94 is arranged so that for fourteenrotations of A'-N'cam 204, leaves I and I 96" engage contact points I96 and I96 respectively, andconsequently fourteen sets of vA-N 'signals'are' transmitted by the quadrant assembly, as previously described. However, upon the completion of the fourteenth rotation of lA-N cam zt hcam I94 'disengages leaf I99 from contact I96 and engages leaf I96 with contact I91 At the same Station identification cams'358, 3,66, 362, 36s

and- 366 rotate with shaft 268 and each moves its-controlled leaf-368, 316, 312, 314 or 316 into engagement with thepoint' 318, 386, 382, 384 or 386. Each of these cams has a peripheral pat- 'tern. correspondingto' that of the call letters of .sa ra'diorange; station. When leaf I9I'I' engages contact I91, any of the-station identification cams 358, 366,662, 36401'366 may'groundv out -the resistance I32 depending upon theposition 'rofrthe contact 354 of selector switch-356. Inthe ucaseshow'n'in Fig.4 it will be seen that'contact 354 engages the fourth terminalof selector switch 356"and therefore cam-364, by causing leaf 314 --"to?;erjigageFanddisengage point 384 in accordance \with its peripheral pattern, shorts tlie resistance -I32" .in. the sameipattern and-consequently the N quadrantssare charged :in accordance with the ppat-tern of cam 36.4, which pattern is that ofthe 15 i call letters of a radio range station. As soon as one of the station identification cams 358, 360, 352, 384 or 366 has shorted out resistance I32 in a pattern corresponding to one set of station identification signals, cam I94 is rotated to its next step and leaf I90 becomes disengaged from contact point I87 but does not engage contact point I98. Therefore the amplifier shown at the lower right of Fig. 4 is biased to such an extent that no plate current flows and consequently the N plates are not charged. However at the same time cam I94 turns to engage leaf I90 with contact point I91 and then one of the station identification cams 358, 360, 362, 364 or 368 may short the resistance I32 in accordance with its pe-' ripheral pattern the effective cam depending upon the position of selector 354. Again if selector 354 is placed as shown cam 364 will short resistance I32 to charge the A plates and pins in accordance with its peripheral pattern.

After one set of station identification signals has been transmitted by the A plates and pins, cams I94 and I94 simultaneously rotate to engage leaf I90 with contact I96 and leaf I90 with contact I96. The A-N cam 204 is thereupon rendered effective to short the resistances I32 and I32 and the quadrant assembly is charged in the usual manner for the required number of A-N signals. 1

This invention therefore provides means whereby the elements of the quadrant assembly may normally be properly charged in an A-N pattern, the A-N pattern being intermittently interrupted, and the quadrant plates and pins for the period of the interruptions will be charged in a pattern corresponding to station identification signals. Selector switch 354 is under the control of the operator and he may select any one of the station identification cams depending upon the signal call letters of the station being simulated.

It has been stated that certain of the legs or equi-signal zones of a real radio range may be provided with auxiliary markers placed a few miles fromv the central transmitting towers which transmit upwardly a 3000 cycle note keyed in dash groups to identify the respective beacons of the range. Referring to Fig. 4 there is disclosed an oscillator 388 connected by conductor 390 to an amplifier 392 which is connected by conductor 394 to conductor 390 which extends upwardly in Fig. 4. Four switches designated generally 398, 400, 402 and 404 are provided, these switches being controlled by cams 406, 408, M

and M2 respectively, which cams are mounted on shaft 208. The peripheral pattern of cam 406 is such that the switch 398 is closed in single dash-groups; cam 408 closes switch 400 in groups of two dashes; cam 4I0 closes switch 402 in groups of three dashes and cam 4I2 closes switch 404 in groups of four dashes. Switch 398 is connected by conductor M4 to terminal E of plug I48 and referring to Fig. 5 it will be seen that terminal E of plug I50, which it will be re called is suitably connected to plug I48, is connected by means of conductor M6 to fan marker .4l8. Switches 400, 402 and 404 are connected by means of conductors 420, 422 and 424 to terminals F, G, and H respectively of plug I48, these terminals in turn being connected to terminals F, G and H, respectively, of plug I50. Terminal F of plug I is connected by conductor 426 to fan marker 428; terminal G is connected by means of conductor 430 to fan marker 432 and terminal H is connected by conductor 434 to fan marker 436.

By virtue of this arrangement fan marker 4I8 is constantly charged with a series of dashes; fan marker 428 is constantly charged with a series of two dash groups; fan marker 432 is constantly charged with a series of three dash groups while fan marker 436 is similarly charged with a series of four dash groups.

Therefore whenever inking wheel 25 passes above any one of the four fan markers a signal corresponding to the pattern of charging of the particular fan marker will be picked up by the inking wheel and will be heard by the student using earphones 216, provided he has properly positioned switch 3I6 as previously described. The received fan marker signal will indicate to him that his assumed position is above the position of the fan marker which will be shown upon the map of the range being simulated. The student will of course have such a map in the fuselage I2.

Reference is now made to Figs. 3 and 9 which disclose the detailed nature of the fan markers. In Fig. 3 the fan marker 428 is shown. It will be seen that this marker comprises the conductor 426 which is surrounded by suitable insulating and grounded shielding material 438. The shielding in turn is held by vertical Bakelite tube 442 which passes through space 220 between conical sections 48 and 50 and is suitably held by the wooden block 42. Sections 48 and 50 may be suitably cut out to allow the positioning of Bakelite tube 442. The extreme upper end of conductor 426 is suitably connected to the inside of cylinder 444. Attached to the upper end of cylinder 444, as by soldering, is plate 448 which has an elliptical shape similar to that shown in Fig. 9. The major axis of plate 448 lies perpendicular to the equi-signal or on-course zone area 220. Further it should be noticed that ends of plate 448 extend downwardly from the center portion thereof.

By virtue of the just disclosed fan marker arrangement the fan marker signals are intercepted only when the inking wheel 25 is immediately thereabove.

It has been previously stated that many real radio ranges are provided with an auxiliary transmitter which transmits upwardly a 3000 cycle note, the field of transmission filling the otherwise present cone of silence. This feature may be simulated in this invention by the means disclosed in Figs. 3 and 4. Referring to Fig. 4 the 3000 cycle wave generated by oscillator 388 is carried by conductor 390 to amplifier 392 and by means of conductors 394 and 450 to terminal I of plug I48 which is connected to terminal I of plug I50 seen in Fig. 5. This last terminal I is connected by conductor 452 to the Z marker pin 454. This pin is located as seen in Fig. 5 in the middle of the four A-N pins I58, I58, I58 and I68. Whenever the inking wheel 25 is directly above Z marker pin 454 the 3000 cycle signal will be picked up instead of a complete absence of signal which would otherwise result from the cancellation of the voltages induced in the four A-N pins.

Referring to Fig, 3 the conductor 452 is shown to be surrounded by insulation 456 and at the upper end of the conductor 452 is the Z marker pin 454. A Bakelite block 453 is mounted in the top of block 42 and pin 454 is suitably held in the center thereof.

Still referring to Fig. 3 the insulated conductor I56 which connects to pin IE8 is shown. Bakepositioned by the use of a screw driver.

lite block 453 is suitably molded to allow conductor I66 to pass upwardly therethrough, and this block is also suitably molded to allow p-in I68, shown in detail in Fig. 10, to be set thereinto. Pin IE8 comprises a cylindrically shaped member I69 made of Bakelite having a slot III. A metallic member I13 has the upper end of wire I66 soldered therein, wire I66 and member I13 are positioned eccentrically of Bakelite cylinder I69, and, therefore, by means of a screw-driver the members I86 and I13 may be moved to lie along the bisector of the cone shaped sector 46. This is necessary because when inking wheel 25 moves along the bisector of a quadrant of a real radio range, a pure A or N only is heard. The other pins I58, I58 and IE8 are identical with the pin IE8 shown in Fig. 10 and are held by insulating block 453 in the same manner.

Reference is now made to Fig. 10 which shows the N transmitting pin designated in Fig. 5 by I68.

Reference is now made to Figs, 11 and 12 which are front and rear elevations respectively of the quadrant assembly. Seen in Fig. 12 is the plug I50 to which reference has been previously made. This plug is provided at the rear of the quadrant assembly to facilitate connecting the cable from the plug I48 of the transmitter shown in Fig. 4. Shown in Fig. 11 are eight slotted adjusting elements designated generally 46!] which may be Each of these adjusting means 460 may be used to control one of the potentiometers I54, I14, I54, I14, I64, I82, I64 or I82 shown in Fig. 5. It will be understood that an adjustment of any of these potentiometers control the potential applied to the A-N plate or pin which is connected through the potentiometer in question to the plug I50 and transmitter shown in Fig. 4. This adjustment may be used to achieve proper relative signal intensities.

In the use of the previously described apparatus the quadrant assembly 26 is positioned and adjusted in the desk I8, as best seen in Fig. 1, so that the signal field set up by the quadrant assembly coincides with the signal field as shown upon the map 20. This step having been accomplished the recorder 22 may be properly oriented with the map 20, in the usual manner, the inking wheel 25 being placed at the exact spot on map where it is assumed that the trainer is located at the beginning of the problem. The inking wheel, which as earlier stated represents the exact spot where the trainer is assumed to be located, will then pick up a signal from the quadrant assembly 26 which exactly simulates the signal that a real plane would intercept were it at a corresponding point in the real radio range being simulated. Thereafter, as the student "fiies the trainer the recorder traces exactly its assumed course and the signals picked up by inking Wheel and heard by the student using the earphones vary exactly as would the signals heard by the pilot in a real plane flying a corresponding course through a real radio range corresponding to the one being simulated.

Numerous changes may be made in the details of this invention without departing from the substance thereof.

I claim:

1. In a radio navigation training device of the type comprising means for establishing a miniature field of force having a pattern corresponding to the radiated field pattern of a real radio range It should be noted that station, the combination of a plurality of chargeable members arranged relative to one another in a manner to establish, when charged, the above-mentioned miniature field, means for intermittently charging said members at a given potential in a predetermined pattern, a second plurality of chargeable members, and means for charging said second members in the same predetermined pattern and at a higher potential, said last mentioned chargeable members being arranged relative to the first mentioned chargeable members so that when charged they establish a field near the center of and stronger than the field established by said first members.

2. In a radio navigation training device of the type comprising means for establishing a miniature field of force having a pattern corresponding to the radiated field pattern of a real radio range station, the combination of a plurality of chargeable members arranged relative to one another in a manner to establish, when charged, the above-mentioned miniature field, means comprising a transformer for intermittently charging said members at a given potential in a predetermined m'anner, a second plurality of chargeable members, and means comprising said transformer for charging said second members in the same predetermined pattern and at a higher potential, said last mentioned chargeable members being arranged relative to the first mentioned chargeable members so that when charged they establish a field near the center of and stronger than the field established by said first members.

3. In a radio navigation training device of the type comprising means for establishing a minia+ ture field of force having a pattern corresponding to the radiated field pattern of a real radio range station, the combination of four chargeable members arranged relative to one another in a manner to establish, when charged, the above-mentioned miniature field, four additional chargeable members, each of said last mentioned members being positioned adjacent a different one of said first mentioned members so that when charged they establish a field near the center of and stronger than the field established by said first members, and means for charging the adjacent members in the same predetermined pattern, said charging means including means for charging each of said second mentioned members at a potential higher than that of said first mentioned members.

4. In a radio navigation training device the combination comprising a plurality of chargeable members insulated one from the others and arranged to form a substantially solid pattern with a central opening and radial spaces when viewed from a given direction, a second plurality of chargeable members insulated one from the others and from said first mentioned chargeable members located within said central opening,

each of said second mentioned members being lo cated adjacent a different one of said first mentioned members, and means for charging the adjacent pairs of members in the same predetermined pattern, said charging means comprising means for charging said centrally located members at a potential higher than said outlying members.

5. A device for teaching navigation by radio comprising, in combination, two pairs of chargeable members and means for charging each pair of members in a predetermined pattern, said charging means comprising a first normally operative pattern determining means for charging 19 eachpair of members in a predetermined pattern, a second normally inoperative pattern determining means, and switching means intermittently operated to render said normally operative pattern determing means inoperative and to render said normally inoperative pattern determining means operative, said switching means comprising means for separately charging each pair of chargeable members in accordance with the pattern of said normally inoperative pattern determining means when said normally operative charging means is rendered inoperative.

6. In a radio navigation training device of the type comprising means for establishing a miniature field of force having a pattern corresponding to the radiated field pattern of a real radio range station, the combination of a plurality of chargeable members arranged relative to one another in a manner to establish, when charged, the above mentioned miniature field, a second plurality of chargeable members arranged relavtive to the first mentioned chargeable members so that when charged they establish an additional field near the center of and stronger than the vfield established by said first members, electronictube means connected to said chargeable members to charge the same, and means for interrupting the plate current of said electronic-tube -means to charge the said chargeable members in a predetermined pattern.

7. A radio navigation training device comprising a plurality of metallic plates each shaped generally like a wedge when viewed from a given direction and all being arranged to form a pattern corresponding generally to the quadrant pattern of a real radio range station when viewed from the same direction, and means for charging said plates in a predetermined pattern, said charging means comprising a first normally operative pattern determining means for charging said plates in a predetermined pattern, a second normally inoperative pattern determining means, and switching means intermittently operated to render said normally operative pattern determining means inoperative and to render said normally inoperative patern determining means operative, said switching means comprising meansfor successively charging certain of said plates in accordance with the pattern of said normally inoperative pattern determining means when said normally operative charging means is rendered inoperative.

THOMAS J. McLAUGI-ILIN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,937,876 Donovan Dec. 5, 1933 2,005,798 Moser June 25, 1935 2,234,828 Luck Mar. 11, 1941 2,352,216 Melvin et al. June 27, 1944 

